Cell wall proteins in white clover: Influence of plant phosphate status

White clover (Trifolium repens L.) plants were grown in either P-containing liquid media, or in media with the sole source of phosphate removed (P-dep rived). At 29 d, plants were harvested and a water-soluble whole tissue ext ract and an ionically-bound (1 M salt-extractable) cell wall protein extrac t made from root and leaf tissue. Acid phosphatase activity was highest in all extracts from root and leaf tissue excised from P-deprived plants, with the biggest difference (4.5-fold) in root cell walls. The smallest fold-in crease was observed in the leaf water-soluble extract. The relative intensi ty of several, although not all, acid phosphatase isoenzymes was also highe st in extracts from P-deprived plants. Up to the limits of detection used, no new acid phosphatase isoenzymes could be detected in extracts from plant s maintained either in P-deprived or P-containing media. The complement of ionically-bound (1 M salt-extractable) cell wall glycoproteins in leaf and root tissue extracts maintained in P-deprived and P-containing media was al so compared. Using SDS-PAGE and immune-recognition with mAb 2.23, a monoclo nal antibody that specifically recognises xylose/fucose mixed-type N-linked glycans, glycoproteins of 30 and 31 kDa were identified which were more pr evalent in the P-deprived root cell wall. Further, a protein of 60 kDa was identified, which was prevalent in root cell wall extracts from plants main tained in P-containing media. The GNA lectin, which detects oligomannose N- linked structures, identified a glycoprotein of 37 kDa which was more preva lent in the P-deprived root cell wall. (C) Elsevier, Paris.